Field of the Invention
The present invention relates to a control apparatus of a vibration actuator, a method for controlling the vibration actuator, a driving apparatus, an imaging apparatus, an interchangeable lens, and an automatic stage.
Description of the Related Art
A vibration motor will be described as an example of a vibration actuator. The vibration motor is a non-electromagnetic driving motor which causes an electric-mechanical energy conversion element, such as a piezoelectric element, to generate high-frequency vibration by applying AC voltage on the element which is connected to an elastic member so as to extract vibration energy as a continuous machine motion.
If a driven member which is a target of driving is to be moved to a target position at high speed in a short time, overshoot may be generated in which the driven member moves over the target position before being stopped. Furthermore, a long period of time may be required for a stabilization time due to a return operation of reversely moving the driven member by a distance of the overshoot.
To address this problem, control apparatuses and a control method described below have been proposed.
Japanese Patent Laid-Open No. 04-075478 discloses a control apparatus including a deceleration control unit which reduces a target speed in a step-by-step manner until a target position is reached. Japanese Patent Laid-Open No. 2000-116159 discloses a control method for increasing a P-gain (a proportional) and an I-gain (an integral term) in PID control calculation before completion of positioning. Japanese Patent Laid-Open No. 3-261380 discloses a control apparatus which performs a stop operation by stopping supply of a driving voltage when a target position is reached after a reverse operation is performed without control immediately before the target position.
However, in the control apparatuses of vibration actuators according to the related arts, it is difficult to enhance responsivity of a stop operation as a driven member moves close to a target position without deteriorating controllability. Specifically, although a stop operation of turning off a voltage or the like may realize deceleration in a short time, controllability of a vibration actuator is deteriorated resulting in poor stop accuracy. If gradual deceleration control is performed, the driven member may be stopped without occurrence of overshoot. However, a long period of time is required for driving time.